High voltage converters, such as voltage source converters or current source converters, are equipped with capacitors that are charged to high voltage levels.
A voltage source converter may for instance be a so-called two-level converter where a capacitor bank is provided between two DC outputs of the converter. The converter may also be a cascaded multilevel converter, made up of a number of cells, in which case each cell may comprise a capacitor.
When not in operation, it is important that these capacitors are discharged.
Furthermore, when not in operation, maintenance may have to be made in an environment where the converter is located, where such an environment may be a so-called valve hall. Before service personnel are allowed into this environment, there may exist a requirement that the capacitors are completely discharged. In order to ensure that this has happened, the capacitors may need to be short-circuited. This means that there may exist a requirement to short-circuit the capacitors of a converter before service personnel are allowed to enter the valve hall.
The invention is directed towards providing such short-circuiting in a safe, reliable and efficient way.